The present invention relates to a method and device for detecting fine particles (contaminants) suspended in a processing chamber of a processing device for semiconductor devices for forming desired films, circuit patterns, and the like on a semiconductor substrate using plasma through etching, sputtering, CVD, or the like. The present invention also relates to a device for processing semiconductor devices equipped with a function for measuring, in real time during processing, particles generated in the processing chamber when films, circuit patterns, and the like are being formed with a plasma processing technology.
Processes using plasma are widely used in semiconductor device processing (production) processes and liquid crystal display device substrate processing (production) processes, e.g., in etching devices.
FIG. 25 shows an example of a processing device that uses plasma in the form of a parallel flat plasma etching device. As shown in FIG. 25, this type of device uses a high-frequency signal from a signal generator 83 to modulate the output potential from a power amp 84. This high-frequency potential is split up using a distributor 85 applied to an upper electrode 81 and a lower electrode 82 disposed parallel to each other in a processing chamber 86. Discharge between the two electrodes 81, 82 generates a plasma 71 from an etching gas. Etching is performed on the workpiece, e.g., a semiconductor substrate (wafer) W.
The high-frequency signal is a signal with a frequency of, for example, 400 kHz. In the etching operation, the progress of etching is monitored and the timing at which to stop etching is detected as accurately as possible so that etching is performed for a predetermined pattern and depth. When the stopping timing is detected, the output from the power amp 84 is stopped and the semiconductor wafer W is ejected from the plasma processing chamber 86.
In this plasma etching device, it is known that the etching reaction product from the plasma operation is deposited on the wall surface of the plasma processing chamber or the electrodes. As time goes by, the product peels off and forms suspended fine particles. As soon as the etching operation is completed and the plasma discharge stops, these suspended fine particles drop onto the wafer to form adhesed particles, leading to negative circuit properties and visual pattern defects. Ultimately, these can lead to reduced yield and reduced reliability of the elements.
Many types of devices for inspecting particles adhered to the surface of the wafer have been proposed and implemented, but these remove the wafer from the plasma processing device to perform inspection. By the time it is known that many particles are present, the processing of another wafer is already begun. This leads to clusters of defects and reduced yield. Also, evaluations performed after processing cannot determine distribution or changes over time in particles inside the processing.
Thus, there is a need in the field of semiconductor fabrication, liquid crystal fabrication, and the like of a technology for performing in-situ real-time monitoring of contamination status in processing chambers.
The sizes of fine particles suspended in the processing chamber range from submicrons to several hundred microns. In the semiconductor field, where integration scale is growing to include 256 Mbit DRAMs (Dynamic Random Access Memory) and 1 Gbit DRAMs, the minimum circuit pattern widths is decreasing to 0.25-0.18 microns. Thus, there is a need to detect sizes of particles down to the order of submicrons.
Conventional technologies for monitoring fine particles suspended in processing chambers (vacuum processing chambers) such as plasma processing chambers include Japanese laid-open patent publication number 57-118630 (background technology 1), Japanese laid-open patent publication number 3-25355 (background technology 2), Japanese laid-open patent publication number 3-147317 (background technology 3), Japanese laid-open patent publication number 6-82358 (background technology 4), Japanese laid-open patent publication number 6-124902 (background technology 5), and Japanese laid-open patent publication number Hei 10-213539 (background technology 6).
The background technology 1 discloses a vaporization device equipped with: means for illuminating a reaction space with a parallel light having a spectrum different from the spectrum of self-emitted light of the reaction space; and means for receiving parallel light illumination and detecting light scattered by fine particles generated in the reaction space.
The background technology 2 discloses a device for measuring fine particles that uses scattering of laser light to measure fine particles adhesed to a semiconductor device substrate surface and suspended fine particles. The device for measuring fine particles is equipped with a laser light phase modulator generating two laser lights modulated at predetermined frequencies having identical wavelengths and mutual phase differences; an optical system intersecting the two laser lights in a space containing the fine particles to be measured; an optical detection system receiving light scattered by the fine particles to be measured in the region where the two laser lights intersect and converting the light into an electrical signal; and a signal processor extracting a signal component from the electrical signal generated by the scattered light where the frequency is identical or twice the frequency of a phase modulation signal from the laser light phase modulator and the phase difference with the phase modulation signal is constant in time.
The background technology 3 discloses a technology for measuring contamination status in a reaction container that includes a step for performing scanning illumination with coherent light and generating scattered light in the reaction container and a step for detecting the scattered light in the reaction container. The scattered light is analyzed to measure the contamination status.
The background technology 4 discloses a particle detector equipped with: laser means generating a laser light; scanner means using the laser light to scan a region in a reaction chamber of a plasma processing tool containing particles to be measured; a video camera generating a video signal of laser light scattered by particles in the region; and means for processing and displaying an image from the video signal.
The background technology 5 discloses a plasma processing device equipped with: a camera device observing a plasma generating region in a plasma processing chamber; a data processing module processing an image obtained from the camera device to obtain desired information; and a control module controlling at least one of the following list to reduce particles based on information obtained by the data processing module: evacuating means; process gas introducing means; high-frequency potential applying means; and purge gas introducing means.
The background technology 6 discloses a fine particle sensor including: a light emitter sending out a light beam illuminating a space to be measured; a detector containing an optical detector and an optical system focusing the scattered light from the space to be measured and directing it to the optical detector, the being set up so that the optical detector generates a signal representing the intensity of the light directed toward the optical detector; a pulse detector connected to the optical detector to analyze the signal from the optical detector, and detecting pulses in the signal from the optical detector; and signal processing means containing an event detector detecting a series of pulses resulting from scattered light generated by fine particles accompanying multiple illuminations by the beam while it moves in the measurement space.
In the conventional technologies described above, a laser light is sent in through an observation window disposed on a side surface of a processing device. A different observation window from the laser entry observation window is disposed on the facing surface or another side surface to allow detection of front-scattering or side-scattering of the laser. Thus, in these systems for detecting front-scattered light and side-scattered light, the illumination optical system and the detection optical system are formed as different units and two observation windows 10a as shown in FIG. 25, for example, are needed to attach these. Also, optical axis adjustments and the like need to be performed for both the illumination and detection optical systems, making operation difficult.
Also, an observation window is almost always disposed on the side surface of a plasma processing chamber to allow monitoring of plasma emission and the like, but in many cases only one observation window is provided. Thus, the conventional methods that require two observation windows cannot be implemented for fabrication devices with a processing chamber that only has one observation window.
Furthermore, in conventional systems that detect front-scattered light and side-scattered light, the illumination beam sent into the processing chamber is rotationally scanned. Observation of fine particle generation over the entire surface of the workpiece such as a wafer requires multiple observation windows and detection optical systems, leading to significant cost increases. Also, providing multiple observation windows and detection optical systems is extremely difficult practically due to space factor restrictions.
Also, in the methods from the conventional technologies described above, a fixed laser light is used to measure a partial region of the wafer, and measuring particles suspended in plasma over the entire surface of the wafer is difficult.
Semiconductor production methods and devices equipped with a function for performing in-situ measurements of particles suspended in a plasma processing chamber over the entire surface of a wafer have been proposed. For example, there is Japanese laid-open patent publication number Hei 9-24359 (background technology 7).
The background technology 7 describes a method for monitoring particles in which a laser light is illuminated in the processing chamber vertically or horizontally or both vertically and horizontally. Laser light scattered by particles in the processing chamber is detected, and particles in the processing chamber are monitored in real time based on the intensity of the detected laser light.
However, in all of these systems, the laser illumination optical system and the scattered light detection optical system are formed separately. For this reason, only devices having at least two observation windows for illuminating the processing chamber with the laser light and detecting the scattered light can be used. In addition, the optical axes of the laser illumination optical system and the scattered light detection optical system must be adjusted separately, making them difficult to use. Japanese laid-open patent publication number Hei 11-251252 (background technology 8) presents a semiconductor production method and device equipped with a function for performing in-situ measurements of particles suspended in a plasma processing chamber over the entire surface of a wafer. A laser beam that is intensity modulated at a frequency different from the plasma excitation frequency is used to illuminate the inside of the plasma processing chamber through an observation window on the plasma processing chamber. Back-scattered light from particles is detected to detect suspended particles.
However, the background technology does not attempt to make the laser light source compact and easy to use.
Eliminating the influence of light reflected from the inner wall surfaces of the processing chamber is one of the issues involved in methods involving detection of back-scattered light. However, the background technology 8 does not take measures to deal with this issue.
In the semiconductor field, where integration is proceeding to the levels of 256 Mbit DRAMs and 1 Gbit DRAMs, the minimum circuit pattern width is being reduced down to 0.25-0.18 microns, creating the need to detect particles with sizes on the order of submicrons. However, with the conventional technologies, separating light scattered by fine particles from plasma emission is difficult, so these technologies have been restricted to use in measuring relatively large fine particles, while detection of fine particles with sizes on the order of submicrons is difficult.
In integrating the laser illumination optical system and the scattered light detection optical system to provide a particle monitor that can be attached to a single observation window, one effective method is to have the laser light propagate backward along the same axis as the illumination laser light so that it returns to the laser illumination optical system and allows back-scattered light to be detected.
Furthermore, making the individual elements used in the monitor more compact is important in providing a compact monitor.
Laser light sources are generally large compared to other optical elements. Also, optical elements tend not to break as long as external physical force is not applied, debris adhesed to the surface is not burnt by the laser light, or the like. Compared to this, laser light sources have short lifespans. Thus, compact and long-lasting semiconductor lasers and solid-state lasers excited by a semiconductor laser are effective for use as laser light sources in in-situ monitors. For uniform particle diameters, the intensity of scattered light generated by particles is proportional to the illumination laser light output and proportional to the square of the wavelength. Thus, compared to semiconductor lasers, solid-state lasers excited by a semiconductor laser in which the wavelength is shortened by non-linear optical crystals is more useful for particle detection through laser scattering.
However, the output and wavelength of semiconductor lasers vary according to changes in the atmospheric temperature and the temperature of the semiconductor crystals, thus requiring temperature control. As higher outputs are used, the amount of generated heat increases, requiring the generated heat to be dissipated externally. Cooling is generally provided through Peltier elements as well as heat-dissipating heat sinks. Compared to the small size of semiconductor lasers, these heat sinks have volumes that are greater by factors of less than ten to several dozen. Based on this, realization of a compact monitor requires a compact laser light source, including the heat sink.
One possible method is to have the laser light source installed externally, with the laser being guided by an optical fiber. Polarizing separation is a useful method for separating the illumination light and the scattered light propagating along the same optical axis, and polarized laser light can be guided by a polarization plane retention fiber. However, with high outputs, the use of thin, core-based polarization plane retention fibers can lead to damage to the entry end surface, leading to an increase in coupling loss. Furthermore, if the laser output is too high, the light can actually be reflected by the fiber rather than entering it. It is possible to increase the beam diameter and guide the beam through a fiber bundle in which multiple fibers are bundled together. However, to retain the polarization plane, the directions of all the individual fiber must be uniform, making this method difficult to implement.
The object of the present invention is to overcome the problems described above and to provide a suspended particle detection device: that integrates a laser illumination optical system and a scattered light detection optical system; that can be attached to a single observation window; that is compact and allows easy optical axis adjustment and the like; and that is equipped with a function for performing in-situ measurements of particles suspended inside a semiconductor production device during semiconductor processing without affecting the processing using a particle monitor that is easily maintained.
In the present invention, an illumination optical system and a detection optical system share the use of a single observation window. An optical system formed as a single unit detects particles suspended inside a processing chamber. Also, the present invention provides a method and device for forming a compact illumination/detection optical system that can be attached in a limited, small space. Also, the present invention provides a highly reliable method and device for precisely detecting very weak particle-scattered light. Also, the present invention provides a method and device for determining particle generation over the entire surface of a body being processed, e.g., a wafer. Also, the present invention provides a processing device for semiconductor devices that includes the above features.
In the present invention, a device for detecting particles suspended in a semiconductor production device includes: a laser light source module; a laser illumination optical system receiving a laser emitted by the laser light source and illuminating a laser inside the semiconductor production device; a scattered light detection optical system detecting a laser scattered by a particle suspended inside the semiconductor production device and illuminated by the scanning performed by the laser illumination optical system; and a signal processing/control module. The laser light source module and the laser illumination optical system are connected by an optical fiber.
According to another aspect of the present invention, a device for detecting particles suspended in a semiconductor production device includes: a laser light source module; a monitoring optical system using output from the laser light source module to illuminate inside the semiconductor production device and detect laser light scattered by a particle suspended inside the semiconductor production device; and a signal processing/control module processing a detection signal from the monitoring optical system. The monitoring optical system is connected to the laser light source module and the signal processing module by optical fibers.
According to another aspect of the present invention, when a desired film-forming/processing operation is being performed on an object being processed in a processing chamber, a laser light guided by an optical fiber from an external laser light source is passed through an observation window and illuminates the inside of the processing chamber. Back-scattered light scattered by particles in the processing chamber passes through the same observation window and is received by a detection optical system. This detection signal is used to determine the quantity, sizes, and distribution of the particles. The results of this are displayed on a display.
According to another aspect of the present invention, the illumination beam illuminating inside the processing chamber through the observation window is rotationally scanned horizontally so that a two-dimensional distribution of particles is determined.
According to another aspect of the present invention, a device for processing semiconductor devices includes: a processing chamber including a window allowing observation inside, a mounting module for mounting a substrate to be processed, and a pressure setting module maintaining a predetermined pressure inside; means for processing plasma generating plasma inside the processing chamber in which the predetermined pressure is maintained and processing the substrate to be processed mounted on the mounting module; a laser light source module disposed outside of the processing chamber; a laser illumination optical system receiving a laser emitted by the laser light source by way of an optical fiber and scanning a laser through the window to illuminate inside the device for processing semiconductor devices; a scattered light detection optical system detecting, through the observation window, scattered light scattered by a particle suspended inside the processing chamber and illuminated by the scanning performed by the laser illumination optical system while the plasma processing means is processing the substrate to be processed; and a signal processing module receiving, by way of an optical fiber, and processing a detection signal from the scattered light detection optical system and outputting information relating to the particle suspended in the device for processing semiconductor devices.
According to another aspect of the present invention, a device for processing semiconductor devices includes; a processing chamber including a window allowing observation inside, a mounting module for mounting a substrate to be processed, and a pressure setting module maintaining a predetermined pressure inside; means for processing plasma generating plasma inside the processing chamber in which the predetermined pressure is maintained and processing the substrate to be processed mounted on the mounting module; a laser light source module disposed outside of the processing chamber; a laser illumination optical system receiving a laser emitted by the laser light source by way of an optical fiber and scanning a laser through the window to illuminate inside the device for processing semiconductor devices; a scattered light detection optical system detecting, through the observation window, scattered light scattered by a particle suspended inside the processing chamber and illuminated by the scanning performed by the laser illumination optical system while the plasma processing means is processing the substrate to be processed; and a signal processing module receiving, by way of an optical fiber, and processing a detection signal from the scattered light detection optical system and outputting information relating to the particle suspended inside the processing chamber for processing semiconductor devices.
According to another aspect of the present invention, a device for processing semiconductor devices includes: a processing chamber including a window allowing observation inside, a mounting module for mounting a substrate to be processed, and a pressure setting module maintaining a predetermined pressure inside; means for processing plasma generating plasma inside the processing chamber in which the predetermined pressure is maintained and processing the substrate to be processed mounted on the mounting module; a laser light source module disposed outside of the processing chamber; a monitoring optical system receiving a laser emitted by the laser light source by way of an optical fiber, scanning a laser through the window to illuminate inside the device for processing semiconductor devices, and detecting, through the observation window, scattered light scattered by a particle suspended inside the processing chamber in which the plasma processing means is processing the substrate to be processed and illuminated by the scanning performed by the laser illumination optical system; and a signal processing module receiving, by way of an optical fiber, and processing a detection signal from the scattered light detection optical system and outputting information relating to the particle suspended inside the processing chamber for processing semiconductor devices.
These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.